Solid propellants

ABSTRACT

1. A solid propellant composition comprising an oxidant of inorganic oxidizing salt and a binder of solid polymer formed by reacting in combination a compound containing 3 aziridinyl groups per molecule and a compound containing only 2 aziridinyl groups per molecule with an uncured polymer of a monomer selected from the group consisting of conjugated dienes having 4 to 12 carbon atoms per molecule, aryl-substituted olefins, pyridine and quinoline derivatives containing at least one member of the group consisting of vinyl and alphamethylvinyl, acrylic acid esters, alkacrylic acid esters, vinylfuran and vinylcarbazole, said uncured polymer containing per molecule at least one acid group of an element selected from the group consisting of carbon, sulfur, silicon, selenium, tin, antimony, tellurium and arsenic.

Unite States Patent [1 1 Malian 1 Dec. 18, 1973 1 SOLID PROPELLANTS John E. Mahan, Bartlesville, Okla.

[73] Assignee: Phillips Petroleum Company,

Bartlesville, Okla.

[22] Filed: Sept. 12, 1960 [2]] App]. No.: 55,602

[75] Inventor:

Primary Examiner-Benjamin R. Padgett Attorney-Qulgg & Oberlin EXEMPLARY CLAIM 1. A solid propellant composition comprising an oxidant of inorganic oxidizing salt and a binder of solid polymer formed by reacting in combination a compound containing 3 aziridinyl groups per molecule and a compound containing only 2 aziridinyl groups per molecule with an uncured polymer of a monomer selected from the group consisting of conjugated dienes having 4 to 12 carbon atoms per molecule, arylsubstituted olefins, pyridine and quinoline derivatives containing at least one member of the group consisting of vinyl and alphamethylvinyl, acrylic acid esters, alkacrylic acid esters, vinylfuran and vinylcarbazole, said uncured polymer containing per molecule at least one acid group of an element selected from the group consisting of carbon, sulfur, silicon, selenium, tin, antimony, tellurium and arsenic.

19 Claims, N0 Drawings soup PROPELLANTS This invention relates to improved solid propellants. In another aspect it relates to an improved method of curing the rubbery binder of a composite propellant and to the resulting propellant composition which has improved physical properties, particularly enhanced elongation at low temperatures.

In the past years or so, great interest has developed in solid propellants for jet propulsion devices such as missiles, rocket motors, gas generators, and the like. One type of solid propellant which has received considerable attention is that of the composite type, a typical composite propellant being one that uses an organic material as the fuel and binder, and a solid oxidant such as ammonium nitrate. In this type of propellant particularly when thepropellant comprises a major proportion of a crystalline oxidizer and a minor proportion of the fuel and binder, the problem is presented of adjusting the physical properties of the propellant because of the small proportion of the binder material. Thus, it is difficult to provide suitable adhesion to the particles of oxidizer and the matrix of binder material is so tenuous that it is difficult to provide sufficient strength and elasticity in the propellant structure. Also in many cases it is desirable and necessary to be able to cast or pour the propellant into a rocket case or mold and then cure to a solid having suitable properties. In addition, since the binder also forms a fuel or part of the fuel it must have suitable chemical properties for this purpose.

It has been disclosed in the copending application of P. S. Hudson and C. C. Bice, Ser. No. 829,462, filed July 24, 1959, now U.S. Pat. No. 3,087,844, that an improved binder for a composite solid propellant can be provided from a synthetic polymer or copolymer containing terminal acidic groups of a synthetic copolymer of an unsaturated carboxylic acid which has been reacted with a tri(aziridinyl)-phosphine oxide or a tri(aziridinyl)phosphine sulfide. In a preferred method of manufacturing a solid propellant grain the uncured propellant composition is poured into a case or mold as a fluid mass and subsequently cured to a resilient solid. The binder in such a casting operation must be quite fluid prior to curing and a high degree of cure is required in order to convert the polymer which is fluid to a solid with acceptable strength. Cured propellant grains must have sufficient mechanical strength to withstand the stress of handling and enormous thrusts encountered in use, as well as resiliency to resist cracking. These properties must be acceptable over a very wide range of temperature and for long periods of time.

I have discovered a method of curing polymer compositions as above described in a manner which increases the elongation of the propellant at relatively low temperatures, for example, 40 to -70 F without substantial sacrifices in tensile strength at the higher temperatures which the propellant encounters during storage and prior to combustion. According to my invention, an improved curing system is used which includes a trifunctional aziridinyl compound as described above in connection with the copending application of Hudson and Bice and in addition a difunctional aziridinyl compound. By regulating the relative proportions of the difunctional and trifunctional aziridinyl compounds I can control the amount of crosslinking which occurs during the curing of the propellant composition, thereby enabling a substantial amount of control over the physical properties of the cured propellant. The curative system of my invention provides great flexibility in the selection of initial components, the mixing and casting conditions as well as the properties of the final product.

It is an object of my invention to provide an improved solid propellant.

Another object of my invention is to provide an improved method of curing the rubbery binder in a composite propellant, said binder being a synthetic polymer on copolymer which contains at least one acidic group per molecule.

Another object is to provide an improved propellant composition which has increased elongation at relatively low temperatures.

Still another object of my invention is to provide a method of controlling the physical properties 'ofa solid propellant by manipulating the relative proportions of ingredients used in the curing system and thereby obtain improvements in low temperature elongation without substantial sacrifice in the tensile strength of the composition at higher temperatures.

Other objects, advantages and features of my invention will be apparent to those skilled in the art from the following discussion.

The novel solid propellants of this invention comprise an inorganic oxidizing salt and a synthetic polymer or copolymer containing terminal acidic groups or a synthetic rubbery copolymer of an unsaturated carboxylic acid which has been reacted with a combination ofa material selected from the group consisting of tri(aziridinyl)phosphine oxides and tri(aziridinyl)hosphine sulfides and a difunctional aziridinyl compound. Particularly useful inorganic oxidizing salts include the ammonium, alkali metal, and alkaline earth metal salts of nitric, perchloric and chloric acids and mixtures thereof such as sodium perchlorate, potassium perchlorate, magnesium perchlorate, ammonium perchlorate, lithium chlorate, strontium chlorate, potassium nitrate, sodium nitrate, calcium nitrate, ammonium nitrate and the like.

The polymers which are utilized in the solid propellants of this invention comprise polymers prepared from a wide variety of materials. These materials include conjugated dienes containing from 4 to 12 carbon atoms and preferably 4 to 8 carbon atoms, such as 1,3-butadiene, isoprene, piperylene, methylpentadiene, 2-ethyl-l,3-butadiene, phenylbutadiene, 3,4-dimethyl- 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, etc. In addition, conjugated dienes containing reactive substituents along the chain can also be employed, such as for example, halogenated dienes, such as chloroprene, fluoroprene, etc. Of the conjugated dienes the preferred material is butadiene, with isoprene and piperylene also being especially suitable. In addition to the conjugated dienes other monomers which can be employed are aryl-substituted olefins, such as styrene, various alkyl styrenes, paramethoxystyrene, vinylnaphthalene, vinyltoluene, and the like; heterocyclic nitrogencontaining monomers, such as pyridine and quinoline derivatives containing at least 1 vinyl or alphamethylvinyl group, such as 2-vinylpyridine, 3-vinylpyridine, 4- vinylpyridine, 3-ethyl-5-vinylpyridine, 2-methyl-5- vinylpyridine, 3,5-diethyl-4-vinylpyridine, etc.; similar monoand di-substituted alkenyl pyridines and the like quinolines; acrylic acid esters, such as methyl acrylate, ethyl acrylate; alkacrylic acid esters, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate,

ethyl ethacrylate, butyl methacrylate; methyl vinyl ether, vinyl chloride, vinylidene chloride, vinylfuran, vinylcarbazole, vinylacetylene, etc., and the like.

The above compounds in addition to being polymerizable alone are also copolymerizable with each other and may be copolymerized to form terminally reactive polymers. In addition, copolymers can be prepared using minor amounts of copolymerizable monomers containing more than one vinylidene group such as 2,4- divinylpyridine, divinylbenzene, 2,3-divinylpyridine, 3,5-divinylpyridine, 2,4-divinyl-6-methylpyridine, 2,3-divinyl--ethylpyridine, and the like.

In the first step of the preparation of the polymers containing terminal acidic groups the monomer or monomers which it is desired to polymerize are contacted with an organo alkali metal compound, preferably an organo polyalkali metal compound. The organo alkali metal compounds contain at least 1 and preferably from 2 to 4 alkali metal atoms, and those containing 2 alkali metal atoms are more often employed. As will be explained herinafter, lithium is the preferred alkali metal.

The organo alkali metal compounds can be prepared in several ways, for example, by replacing halogens in an organic halide with alkali metals, by direct addition of alkali metals to a double bond, or by reacting an organic halide with a suitable alkali metal compound.

The organo alkali metal compound initiates the polymerization reaction, the organo radical being incorporated in the polymer chain and the alkali metal being attached terminally to at least one end of the polymer chain. When employing polyalkali metal compounds an alkali metal is attached terminally at each end of the polymer chain. The polymers in general will be linear polymers having two ends; however, polymers containing more than two ends can be prepared within the scope of the invention. These polymers can be represented by the general formula QY, where Q comprises the polymer as previously described and Y is an alkali metal, n being an integer of l to 4. The general reaction Butadlcnc Organo alkali metal compound or combinations thereof.

A specific example is:

In the specific example l,4-addition of butadiene is shown; however, it should be understood that l,2- addition can also occur.

While organo compounds of the various alkali metals can be employed in carrying out the polymerization, by far the best results are obtained with organolithium compounds which give very high conversions to the terminally reactive polymer. With organo compounds of the other alkali metals, the amount of monoterminally reactive polymer, that is, polymer having alkali metal at only one end of the chain is substantially higher. The alkali metals, of course, include sodium, potassium, lithium, rubidium, and cesium. The organic radical of the organo alkali metal compound can be an aliphatic, cycloaliphatic or aromatic radical. For example, monodiand polyalkali metal substituted hydrocarbons can be employed including methyllithium, n-butyllithium, n-decyllithium, phenyllithium, naphthyllithium, ptolyllithium, cyclohexyllithium, 4-butylphenylsodium, 4-cyclohexylbutylpotassium, isopropylrubidium, 4- phenylbutylcesium, 1,4-dilithiobutane, 1,5-dipotassiopentane, l,4-disodio-2-methylbutane, l ,6- dilithiohexane, 1,10-dilithiodecane, l ,15 -dipotassiopentadecane, l ,20-dilithioeicosane, l ,4-disodio-2- butene, l,4-dilithio-2-methyl-2-butene, l,4-dilithio-2- butene, 1,4-dipotassio-2-butene, dilithionaphthalene, disodionaphthalene, 4,4-dilithiobiphenyl, disodiophenanthrene, dilithioanthracene, l ,2-dilithiol l diphenylethane, l,2-disodio-l ,2,3-triphenylpropane, 1 ,2-dilithio-l ,2-diphenylethane, l ,2-dipotassiotriphenylethane, l,2-dilithiotetraphenylethane, l ,2-dilithio-l phenyll -naphthylethane, l,2-dilithio-l ,2- dinaphthylethane, l,2-disodiol l -diphenyl-2- naphthylethane, 1,2-dilithiotrinaphthylethane, l,4-dilithiocyclohexane, 2,4-disodioethylcyclohexane, 3,5- dipotassio-n-butylcyclohexane, 1,3,5-trilithiocyclohexane, l-lithio-4-(2-lithiomethylphenyl)butane, l,2- dipotassio-3-phenylpropane, l,2-di(lithiobutyl)benzene, l,3-dilithio-4-ethylbenzene, 1,4-dirubidiobutane, l,8-dicesiooctane, 1,5, l 2-trilithiododecane, 1,4,7- trisodioheptane, 1 ,4-di( l ,2-dilithio-2- phenylethyl)benzene, l,2,7,8-tetrasodionaphthalene, 1,4,7, 1 O-tetrapotassiodecane, 1,5-dilithio-3-pentyne, l,8-disodio-5-octyne, l,7-dipotassio-4-heptyne, 1,10- dicesio-4-decyne, and 1,1 l-dirubidio-S-hendecyne, l,- 2-disodio-l,2-diphenylethane, dilithiophenanthrene, l,2-dilithiotriphenylethane, l,2-disodio-l ,1- diphenylethane, dilithiomethane, 1,4-dilithiol ,1 ,4,4- tetraphenylbutane, 1,4-dilithiol ,4-dinaphthylbutane, and the like.

While the organo alkali metal initiators in general can be employed, certain specific initiators give better results than others and are preferred in carrying out the preparation of the terminally reactive polymers. For example, of the condensed ring aromatic compounds the lithiumanthracene adduct is preferred, but the adducts of lithium with naphthalene and biphenyl can be employed with good results. Of the compounds of alkali metals with polyaryl-substituted ehtylenes, the preferred material is l,2-dilithio-l ,Z-diphenylethane (lithium-stilbene adduct). Another preferred initiator is the dilithium adduct of conjugated dienes containing from 1 to 7, preferably 1 to 5 diene units per molecule. Especially suitable is the dilithium adduct of 2,3-dimethyll ,3-butadiene.

Ordinarily the dilithio compounds are preferred as being more effective in promoting the formation of terminally reactive polymers. The polymers thus formed are especially well suited for use in our invention as binders for castable rocket propellant mixtures since such materials can be cured from the liquid state to rubbery solids. The organo dialkali metal compounds which have been set forth as being preferred, are those which when prepared contain a minimum of the monoalkali metal compound.

The amount of initiator which can be used will vary depending on the polymer prepared, and particularly the molecular weight desired. Usually the terminally reactive polymers which are liquids have molecular weights in the range of 1,000 to about 20,000. Depending upon the monomers employed and the amount of initiator used, semi-solid and solid terminally reactive polymers can be prepared. Usually the initiator is used in amounts between about 0.25 and about 100 millimoles per 100 grams of monomer.

Preparation of the polymers containing terminal alkali metal atoms is generally carried out in the range of 5 between 1OO and +l50 C., preferably between -75 and +75 C. The particular temperatures employed will depend on both the monomers and the initiators used in preparing the polymers. For example, it has been found that the organolithium initiators provide more favorable results at elevated temperatures whereas lower temperatures are required to effectively initiate polymerization to the desired products with the other alkali metal compounds. The amount of initiator employed can vary but is preferably in the range of between about i and about 30 millimoles per 100 grams of monomers. It is preferred that the polymerization be carried out in the presence of a suitable diluent, such as benzene, toluene, cyclohexane, methylcyclohexane, xylene, n-butane, n-hexane, n-heptane, isooctane, and the like. Generally, the diluent is selected from hydrocarbons, e.g., paraffms, cycloparaffins, and aromatics containing from 4 to carbon atoms per molecule. As stated previously, the organodilithium compounds are preferred as initiators in the polymerization reaction since a very large precentage of the polymer molecules formed contain two terminal reactive groups, and also the polymerization can be carried out at normal room temperatures. This is not to say, however, that other organo alkali metal initiators cannot be employed; however, usually more specialized operation or treatment is required with these materials, including low reaction temperatures. Since it is desirable to obtain a maximum yield of terminally reactive polymer, it is within the scope of the invention to use separation procedures, particularly with alkali metal initiators other than lithium compounds, to separate terminally reactive polymer from the polymer product.

The terminally reactive polymers prepared as hereinabefore set forth contain an alkali metal atom on at last one end and preferably on each end of the polymer chain and the organic radical of the initiator is present in the polymer chain. These terminally reactive polymers when treated with suitable reagents such as carbon dioxide, sulfuryl chloride, etc., and hydrolyzed provide polymers containing terminal acid groups. The acidic groups include groups such as SOH, SO H, $0 M, COOH, SeO l-l, SeO l-l, SiO H, SnO H, SbO H, SbOl-l, SbO li TeO H, TeO H, AsO H, AsOH, AsO H Mon-1,. The following reactions present examples of specific methods which can be employed to introduce the terminal acid groups. In these equations 0 designates a polymer chain.

Reaction of terminally reactive polymer containing alkali metal atoms with the acid forming reagents can be carried out over a wide range of temperatures, for example 75 C. to +75 C., and preferably utilizing an amount of reagent in excess of stoichiometric.

The monomers hereinbefore described for use in preparation of terminal reactive polymers containing alkali metal atoms can also be reacted with unsaturated carboxylic acids to provide liquid polymers suitable for use in carrying out the invention. Unsaturated carboxylic acids which can be employed include acids containing up to 36 carbon atoms, from 1 to 5 double bonds and 1 or 2 carboxyl groups. Also included are the so-called dimerized acids, i.e., where two molecules of an acid are linked by destroying one of the double bonds. Illustrative of specific acids which can be used are acids such as acrylic acid, methacrylic acid, itaconic acid, vinylacetic acid, palmitoleic acid, oleic acid, ricinoleic acid, arachiodnic acid, erucic acid, selacholeic acid, fumaric acid, maleic acid, and the like. Reaction of the monomer with the unsaturated carboxylic acid can be carried out over a wide range of temperatures depending on the particular monomer and the particular acid employed; e.g. at temperatures between about 50 and about I OO-C. The amount of acid employed in the reaction can vary to provide polymers having an acid equivalence of from as low as 0.005 to as high as 0.2 equivalents per grams of polymer product.

The tri(aziridinyl)phosphine oxides and sulfides employd in the invention can be represented by the formula i,

wherein X is selected from the group consisting of oxygen and sulfur, P is phosphorus, the Rs are radicals containing up to a total of 20 carbon atoms selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl, alkaryl and aralkyl radicals and the Rs can be unlike. Specific phosphine reactants which can be used include tri( l-aziridinyl)phosphine oxide, tri(Z-methyll-aziridinyl)phosphine oxide, tri(2,3-dimethyl-laziridinyl)phosphine oxide, tri(Z-isopropyl-laziridinyl)phosphine oxide, tri(2-methyl-3-ethyl-laziridinyl)phosphine oxide, tri(2-isopropyl-1- aziridinyl)phosphine oxide, tri(2-methyl-3-n-butyl-laziridinyl)phosphine oxide, tri(Z-hexyl-1-aziridinyl)- phosphine oxide, tri(2,3-diheptyl-1- aziridinyl)phosphine oxide, tri(2-methyl-3-octyl-laziridinyl)phosphine oxide, tri(2-ethyl-3-decyl-1- aziridinyl)phosphine oxide, tri(Z-dodecyl-laziridinyl)phosphine oxide, tri(2-methyl-3-tridecyl-1- aziridinyl)phosphine oxide, tri(2-ethyl-3-octadecyl-laziridinyl )phosphine oxide, tri( Z-eicosyll aziridinyl)phosphine oxide, tri( 2-methyl-3- cyclopentyl-1aziridinyl)phosphine oxide, tri(Z-ethyl- 3-cyclohexyl-l-aziridinyl)phosphine oxide, tri[2-nbutyl-3-(4-methylcyclohexyl) l-aziridiny11phosphine oxide, tri(2-phenyl-l-aziridinyl)phosphine oxide, tri(2-phenyl-3-tetradecyll-aziridinyl)phosphine oxide, tri(2,3-diphenyl-1-aziridinyl)phosphine oxide, tri(- 2-tert'butyl-3-phenyl-l-aziridinyl)phosphine oxide, tri- 2-ethyl-3-( l-naphthyl) 1 -aziridinyl]phosphine oxide, tri[2-n-propyl-3-(2-naphthyl)l-aziridiny11phosphine oxide, oxide, tri(2-nonyl-3-benzyl-l-aziridinyl)phosphine oxide, tri[ 2-n-propyl-3-(2-phenylethyl) laziridinyl]phosphine oxide, tri[2-methyl-3-(4-methylphenyl)l-aziridinyl]phosphine oxide, tri[2-ethyl-3-(3- n-propylphenyl) l -aziridinyl]phosphine oxide, tri[ 2- tri(2-methyl-3-benzyl-l-aziridinyl)phosphine ployed in the combined curative system of this invention are defined by the formula R 'R HIC chi NXN HC CH A R" wherein X is selected from the group consisting of carbonyl, phenyl phosphoryl, phenyl thiophosphoryl, sulfoxyl or sulfonyl and each R and R is hydrogen or an alkyl group containing from 1 to 4 carbon atoms. In the preferred species X is phenyl phosphoryl or sulfoxyl, R is hydrogen and R is methyl. Examples of suitable difunctional aziridinyl compounds are: phenyl-bis(2- methyl-l-aziridinyl)-phosphine sulfide, phenyl-bis(2- methyl- 1 -aziridinyl)-phosphine oxide, ethyl-l-aziridinyl)-phosphine oxide, phenyl-bis(2- methyl-3-ethyl-l-aziridinyl)-phosphine oxide, phenylbis(2-butyl-l-aziridinyl)-phosphine oxide, bis( 2-methyl-l-aziridinyl) sulfoxide, bis(2-propyl-l-aziridinyl) sulfoxide, bis(2-methyl-3-propyl-l-aziridinyl) sulfoxide, (2-methylaziridinyl-Z-butyl-l-aziridinyl) sulfoxide, bis( l-aziridinyl) sulfone, bis( 2-methyl-l-aziridinyl) sulfone, bis(2-ethyl l-aziridinyl) sulfone, bis(2-propyl-laziridinyl) sulfone, bis(2-ethyl-3-propyl-l-aziridinyl) sulfone, (2-methylaziridinyl-Z-ethyl-l-aziridinyl) sulfone, bis( l,2-propylene)-l ,3-urea, bis( l,2-pentylene)- 1,3-urea, bis(4,5-octylene)-l,3-urea, and the like.

In accordance with my invention a terminally reactive liquid polymer is admixed with a trifunctional aziridinyl compound, a difunctional aziridinyl compound and an inorganic oxidizing salt, after which the mixture is suitably increased in temperature, such that reaction occurs between the polymer and the aziridinyl compounds to provide a solid propellant structure. In the preparation of the binder from liquid polymer, the polymer and aziridinyl compounds are placed in a suitable dispersant-type mixer and thoroughly mixed for a period of l to minutes. The oxidizer, which is finely powdered to a size in the range of from 1 to 200 microns, is then added and mixing is continued for a period of to 45 minutes under vacuum. During the latter mixing step, the temperature is gradually increased to a temperature between about 100 to 300 F, preferably between about l50 and 200 F. The material at this stage is a viscous slush, which is then poured into a rocket case or suitable mold. The filled mold is then phenyl-bis( 2- placed in an oven and cured for 24 to 48 hours or more at temperatures in the range of 150 to 200 F. Semisolid polymers can be blended with the aziridinyl compounds and oxidizer, and the mixture extruded to form a curable propellant grain.

In general the curing agents will comprise from 10 to percent difunctional compounds and preferably from 30 to 70 percent difunctional aziridinyl compound. The total amount of curative used is preferably about stoichiometric to somewhat above stoichiometric, for example, about percent of the stoichiometric amount of curative based upon the acid equivalents of the polymers. With polymers in the lower range of equivalents amounts of curative up to percent of stoichiometric can be readily employed and with the polymers in the higher range of acid equivalents, as low as 10 percent of the stoichiometric amount of curative is effective. When using the lower amounts of curative the excess carboxyl groups, for example, are useful in developing adherence to surfaces such as the rocket cases, oxidizer particles or to glass or ceramic surfaces.

The solid propellants of this invention can contain in addition to the binder fuel a powdered metal such as aluminum and various compounding ingredients commonly employed in making composite propellants, such as plasticizers oxidation inhibitors, reinforcing agents, wetting agents modifiers, vulcanizing agents, curing agents, accelerators, burning rate catalysts, and the like. The propellant composition can be formed into a grain having any desired shape or geometry, such as grains of the internal, external and internal-external burning types. These grains can be molded or extruded and can be restricted with any suitable and well-known restricting material, such as rubber.

The propellants of this invention can contain a powdered metal, for example, aluminum, boron, magnesium, beryllium, and the like. Alloys can also be used such as the aluminum alloys of boron, magnesium, manganese, copper and the like. Silicon can also be utilized and the term metal is used herein to include silicon. Generally the components of the solid propellant compositions of this invention are present in the relative amounts set forth in Table I.

TABLE I Component Weight per cent Inorganic oxidizing salt 75-90 Acidic polymer l025 Powdered metal 0-25 Various types of compounding ingredients including fillers such as carbon black and mineral fillers can be incorporated in the polymer prior to reaction of the polymer with the phosphine reactant. Where it is desired to closely control the burning rate of the propellant composition suitable burning rate catalysts can be incorporated therein. These catalysts include materials such as ferrocyanides sold under various trade names, such as Prussian blue, Steel blue, Bronze blue, Turnbull's blue, Chinese blue, New blue, Antwerp blue, Mineral blue, Paris blue, Berlin blue, Hamburg blue, Williamson blue, and the like. Other useful burning rate catalysts include copper chromite, ammonium dichromate, potassium dichromate, sodium dichromate and the like.

The advantages of my invention are illustrated by the following examples. In these examples, specific conditions and materials given are presented as being typical and should not be construed to limit my invention unduly.

EXAMPLE I Butadiene was polymerized in the presence of a dilithium adduct of 2,3-dimethyl-l ,B-butadiene according to the following recipe.

Parts by weight Butadiene 100 Toluene 1200 l Lithium di-methyl-butadiene adduct, 20 millimoles Temperature, F 122 Time, hours 1 The butadiene and then the initiator were charged to the toluene and the mixture was agitated in a constant temperature bath. The conversion was 100 percent. The polymer was then carbonated by contacting the solution with carbon dioxide, dilute HCl was added, the polymer was washed with water and dried on a rotary drier. The resulting polymer had a viscosity of 630 poises and a carboxy content of 1.33 percent. This carboxy-telechelic polymer was compounded with ammonium perchlorate and a curative system according to the recipes for propellant compositions A and B as shown below:

Propellant Weight Per Cent A B Carboxy-tclechclie polymer 19.37 19.55 Tri(2-methyl-l-aziridinyl) phosphine oxide 0.24 0.45 Phenyl-bis(2-methyl-l-aziridinyl) phosphine oxide 0.39" Ammonium perchlorate 80.00 80.00 (I) per cent of stoichiometric (2) 101 per cent of stoichiometric 35 (3) The ammonium perchlorate is a /30 mixture of 200 microns/18 microns particle size material.

The polymer of recipe A was cured for 72 hours at 160 F and the propellant B was cured 96 hours at 160 F. The physical properties of the resulting propellant compositions were determined over a range of temperatures. These results are given in Table II.

EXAMPLE I1 Butadiene and styrene are copolymerized in the presence of a dilithium adduct of 2,3-dimethyl-1,3- butadiene as shown in the following recipe.

Parts by Weight Butadiene Styrene 10 Cyclohexanc 780 Lithium dimcthybbutadiene adduct,

millimoles 20 Temperature. "F 122 Time, hours 1 Monomers were charged to the cyclohexane followed by the initiator and the mixture was agitated in a constant temperature bath for 1 hour. The conversion was 100 percent. The polymer was then carbonated with carbon dioxide to saturation, dilute HCl was added and the polymer was washed with water. One per cent of an antioxidant, phenyLbeta-naphthylamine, was added and the polymer was dried on a rotary drier. The resulting carboxy-telecheic copolymer of butadiene and styrene had a viscosity of 1173 poises and a carboxy content of 1.16 percent. This carboxytelechelic copolymer was compounded with curative and ammonium perchlorate as shown in the recipes below for propellants C and D.

Propellant (Weight Per Cent) C Carboxy-tclechclic copolymer 19.46 19.58 Tri(2-methyl-l-aziridinyl) phosphinc oxide 0.21 0.42" Phenyl-bis(2 methyl-l-aziridinyl) phosphinc oxide 0.33

Ammonium perchloratc 80.00 80.00

0 (1) 55 per cent of stoichiometric (2) per cent of stoichiomctric (3) The ammonium perchlorate is a 70/30 mixture of 200 microns/18 microns particle size material.

TABLE 11 Sm* (psi) Sb* (psi) Em* Elf E* (psi) Temperature F.) A B A B A B A B A B S m stress at yield.

Sb stress at break.

Em elongation at yield. Eb elongation at break. E Young's modulus.

*See Method for Determining the Tensile Properties of Solid Rocket Propellants, Part 11, Solid Pro pellant Information Agency, .lohn Hopkins University, Silver Spring, Maryland, February 1957.

The above data demonstrate that the combined curative of triaziridinyl compounds and difunctional aziridinyl compounds permits substantial improvements in elongation of propellant composition and also improvement in the tensile strength of the composition at The propellant C was cured for 72 hours at F and propellant D was cured for 96 hours at 160 F. Physical properties of these propellants were determined ovcr a range of temperatures as in Example 1 and 65 the results are shown in Table 111.

TABLE Ill 5111* (psi) Sb* (psi) Em* Eb* E* (psi) Temperature F C D C D C D C D C D Sm-stress at yield. Sb-stress at break. Em-elongation at yield. lib-elongation at break. E- Young's modulus.

*See Method for Determining the Tensile Properties of Solid Rocket Propellants," Part 11, Solid Propellant Information Agency, John Hopkins University, Silver Spring, Maryland, February 1957.

EXAMPLE 111 Butadiene was polymerized in the presence of a diliphosphine oxide, with exception that in propellant composition G the difunctional curative employed was bis( l,2-propylene)-l ,3-urea. In all compositions weight per cent of the propellant was ammonium perchlorate with the exception that in propellant J weight per cent of the composition was ammonium perchlorate. Propellant I was cured for 108 hours at 160 F and the other propellants were cured for 96 hours at 160 F. Total amount of curative employed varied from to 122 per cent of stoichiometric as shown in Table IV with the relative proportions of diand trifunctional curatives being varied as shown in this table. Physical properties of the propellants were determined over a range of temperatures and results are shown in Table IV.

TABLE IV Curative. percent stoichiometric Sm Em E Tri Di Total 170 F 70 F -40 F 170 F 70 F -40 F 170 F -40 F *Cured with carbonyl 2-methylaziridine as the difunctional curative.

thium adduct, 2,3-dimethy1-1,3-butadiene, according to the following recipe:

Parts by Weight Butadiene 100 Cyclohexane 1000 Lithium dimethyl-butadiene adduct, millimoles 22 Temperature. "F 122 Time, hours 2 Butadiene was charged to the cyclohexane followed by the initiator and the mixture was maintained in a constant temperature bath for 2 hours with agitation. Conversion was 100 percent and the polymer was carbonated to saturation with carbon dioxide. Dilute HCl was added and the polymer was washed with water. One per cent of an antioxidant, phenyl-betanaphthylamine, was added and the polymer was dried on a rotary drier. The resulting carboxy telechelic polybutadiene had a viscosity of 486 poises and a carboxy content of 1.37 percent. The resulting carboxy telechelic polybutadiene was employed to prepare five propellant compositions by mixing the polymer with ammonium perchlorate and as a curative, a mixture of tri- (Z-methyl-1-aziridinyl)phosphine oxide and a difunctional curative, pheny1-bis(2-methylaziridinyl)- The above data show that the physical properties of the final propellant can be varied considerably by manipulating the relative proportions of the diand triaziridinyl compounds employed to cure the propellant system. In general it is seen that the tensile strength of the propellant increases as the ratio of difunctional to trifunctional aziridinyl compounds increases. It has been observed that when only a trifunctional aziridinyl compound is employed, as the curative level decreases, the tensile strength of the propellant decreases while the elongation of the composition increases. However, when a mixture of the difunctional and trifunctional aziridinyl compound is employed the amount of trifunctional curative can be decreased to obtain improvements in elongation of the composition without substantially sacrificing the tensile strength of the propellant and at times even tensile strength is improved.

As will be apparent to those skilled in the art from the above discussion and examples, modifications and variations can be made in my invention without departing from the spirit or scope thereof.

l. A solid propellant composition comprising an oxidant of inorganic oxidizing salt and a binder of solid polymer formed by reacting in combination a compound containing 3 aziridinyl groups per molecule and a compound containing only 2 aziridinyl groups per molecule with an uncured polymer of a monomer selected from the group consisting of conjugated dienes having 4 to 12 carbon atoms per molecule, arylsubstituted olefins, pyridine and quinoline derivatives containing at least one member of the group consisting of vinyl and alphamethylvinyl, acrylic acid esters, alkacrylic acid esters, vinylfuran and vinylcarbazole, said uncured polymer containing per molecule at least one acid group of an element selected from the group consisting of carbon, sulfur, silicon, selenium, tin, antimony, tellurium, and arsenic.

2. The composition of claim 1 wherein said uncured polymer is a liquid polymer containing 1 to 4 of said acid groups terminally positioned on the molecule.

3. The composition of claim 1 wherein said uncured polymer is a copolymer of said monomer with an unsaturated carboxylic acid having a maximum of 36 carbon atoms, from 1 to 4 double bonds, and from 1 to 2 carboxy groups per molecule.

4. A solid propellant composition comprising an oxidant of inorganic oxidizing salt and a binder of synthetic solid polymer formed by reacting in admixture with said salt an uncured polymer of a monomer selected from the group consisting of conjugated dienes having 4 to 12 carbon atoms per molecule, arylsubstituted olefins, pyridine and quinoline derivatives containing at least one member of the group consisting of vinyl and alphamethylvinyl, acrylic acid esters, alkacrylic acid esters, vinylfuran and vinylcarbazole, said uncured polymer containing per molecule at least one acid group of an element selected from the group consisting of carbon, sulfur, silicon, selenium, tin, antimony, tellurium, and arsenic with a combination of a trifunctional material having the formula wherein X is selected from the group consisting of oxygen and sulfur, P is phosphorus, and each R is selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl, alkaryl, and aryl radicals, both R's containing up to a total of 20 carbon atoms, and a difunctional material having the formula wherein X is selected from the group consisting of carbonyl, phenyl phosphoryl, phenyl thiophosphoryl, sulfoxyl, and sulfonyl, and each R is selected from the group consisting of hydrogen and alkyl radicals of 1 to 4 carbon atoms.

5. The composition of claim 4 wherein said uncured polymer is a liquid polymer of a conjugated diene having 4 to 12 carbon atoms per molecule and contains 2 to 4 terminal carboxy groups.

6. The composition of claim 4 wherein said uncured polymer is a copolymer of a conjugated diene having from 4 to 12 carbon atoms per molecule with an unsaturated carboxylic acid having a maximum of 36 carbon atoms, from 1 to 5 double bonds and from 1 to 2 carboxyl groups.

7. A solid propellant composition comprising about to weight per cent inorganic oxidizing salt and about 10 to 25 weight per cent ofa synthetic solid polymer formed by reacting in admixture with said salt an uncured polymer of a conjugated diene having from 4 to 12 carbon atoms per molecule, said uncured polymer containing at least one carboxyl group per molecule, with at least about a stoichiometric amount based on the acid equivalents of a combination curative containing 10 to 90 weight per cent of a trifunctional material having the formula wherein X is selected from the group consisting of oxygen and sulfur, P is phosphorus, and each R is selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl, alkaryl, and aryl radicals, both Rs containing up to a total of 20 carbon atoms, and 10 to 90 weight per cent of a difunctional material having the formula wherein X is selected from the group consisting of carbonyl, phenyl phosphoryl, phenyl thiophosphoryl, sulfoxyl, and sulfonyl, and each R is selected from the group consisting of hydrogen and alkyl radicals of l to 4 carbon atoms.

8. The composition of claim 7 wherein said polymer is a liquid polymer of a conjugated diene having 4 to 12 carbon atoms per molecule and contains 2 to 4 terminal carboxy groups.

9. The composition of claim 8 wherein said conjugated diene is butadiene, said trifunctional material is tri(Z-methyl-l-aziridinyl) phosphine oxide and said difunctional material is phenyl-bis( 2-methyll -aziridinyl) phosphine oxide.

10. The composition of claim 7 wherein said salt is ammonium perchlorate, said polymer is polybutadiene prepared in the presence of an organodilithium initiator and containing two terminal carboxy groups per molecule, said trifunctional material is tri( 2-methyl-laziridinyl) phosphine oxide, and said difunctional material is bis( 1 ,2-propylene )-l ,3-urea.

11. The composition of claim 7 wherein said salt is ammonium perchlorate, said polymer is polybutadiene prepared in the presence of an organodilithium initiator and containing two terminal carboxy groups per molecule, said trifunctional material is tri(2-methyl-laziridinyl) phosphine oxide, and said difunctional material is bis(2-methyl-l-aziridinyl) sulfoxide,

12. A method of preparing a solid propellant composition which comprises forming a mixture of inorganic oxidizing salt and an uncured polymer containing at least one acid group per molecule, and curing said polymer by reacting same with a combination of a compound containing 3 aziridinyl groups per molecule and a compound containing only 2 aziridinyl groups per molecule, said uncured polymer being a polymer of a monomer selected from the group consisting of conjugated dienes having 4 to 12 carbon atoms per molecule, aryl-substituted olefins, pyridine and quinoline derivatives containing at least one member of the group consisting of vinyl and alphamethylvinyl, acrylic acid esters, alkacrylic acid esters, vinyl-furan and vinylcarbazole, and said acid group being of an element selected from the group consisting of carbon, sulfur, silicon, selenium, tin, antimony, tellurium, and arsenic.

13. A method of preparing a solid propellant composition which comprises forming a mixture of an inorganic oxidizing salt, an uncured polymer of a monomer selected from the group consisting of conjugated dienes having 4 to 12 carbon atoms per molecule, arylsubstituted olefins, pyridine and quinoline derivatives containing at least one member of the group consisting wherein X is selected from the group consisting of oxygen and sulfur, P is phosphorus, and each R is selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl, alkaryl, and aryl radicals, both Rs containing up to a total of carbon atoms and a difunctional material having the formula wherein X is selected from the group consisting of carbonyl, phenyl phosphoryl, phenyl thiophosphoryl, sulfoxyl, and sulfonyl, and each R is selected from the group consisting of hydrogen and alkyl radicals of l to 4 carbon atoms, and heating said mixture at a temperature in the range of 100 to 300 F for sufficient time to cure said polymer and form a solid propellant.

14. The composition of claim 13 wherein said uncured polymer is aliquid polymer containing 1 to 4 of said acid groups terminally positioned on the molecule.

15. The method of claim 13 wherein said uncured polymer is a copolymer of said monomer with an unsaturated carboxylic acid having a maximum of 36 carbon atoms, from 1 to 5 double bonds and from 1 to 2 carboxyl groups.

16. A method of preparing a solid propellant composition which comprises forming a mixture containing about to weight per cent inorganic oxidizing salt, about 10 to 25 weight per cent of a liquid polymer of a conjugated diene containing 4 to 12 carbon atoms per molecule, said polymer having been prepared in the presence of organo dilithium initiator and containing two terminal carboxy groups per molecule, and at least about a stoichiometric amount based on the acid equivalents of a combination curative containing 10 to 90 weight per cent of a trifunctional material having the formula wherein X is selected from the group consisting of oxygen and sulfur, P is phosphorus, and each R is selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl, alkaryl, and aryl radicals, both Rs containing up to a total of 20 carbon atoms, and 10 to 90 weight per cent of a difunctional material having the formula wherein X is selected from the group consisting of carbonyl, phenyl phosphoryl, phenyl thiophosphoryl, sulfoxyl, and sulfonyl, and each R is selected from the group consisting of hydrogen and alkyl radicals of l to 4 carbon atoms, and heating said mixture at a temperature in the range of to 300 F for sufficient time to cure said polymer and form a solid propellant.

17. The method of claim 16 wherein said conjugated diene is butadiene, said trifunctional material is tri(2-methyl-l-aziridinyl) phosphine oxide and said difunctional material is phenyl-bis(2-methyll -aziridinyl) phosphine oxide.

18. The method of claim 16 wherein said conjugated diene is butadiene, said trifunctional material is tri(2-methyl-l-aziridinyl) phosphine oxide and said difunctional material is bis( l-2propylene)-l,3-urea.

19. The method of claim 16 wherein said mixture is poured as a slush into a rocket case and cured in situ.

umll'nu D'L'A'L'Jib rAl'luN'l' Uh'blGlS CERTIFICATE OF CORRECTION Patent No0 3,779,821; John E. Mahan Dated De It is certified that error appears in the above-=identified patent and that Letters Patent are hereby corrected as shown below:

Column 12, line 6'7, compound containing 3 aziridinyl groups per molecule and a containing only 2 aziridinyl groups per molecule" should read triaziridinyl selected from the group consisting of triaziridinyl phosphine oxides and triazi phosphine sulfides wherein each aziridine ring carbon atom is bonded to two mem from the group consisting of hydrogen, alkyl, cycloallcyl, aryl, alkaryl, and ar containing up to a total of 20 carbon atoms for each aziridine ring, and a diaz compound containing two aziridinyl radicals joined through a divalent radical s from the group consisting of carbonyl, phenylphosphoryl, phenylthiophosphoryl s and sulfonyl, each aziridine ring carbon atom being bonded to two members sales the group consisting of hydrogen and alkyl radicals containing 1 to 1; carbon at Golunnl5, line A, claim 12 should read:--A method of preparing a solid propellai which comprises forming a mixture of inorganic oxidizing salt and an uncured pol containing at least 1 acid group per molecule, and curing said polymer by react:

, vwith a combination of a triaziridinyl compound selected from the group consistii aziridinyl. phosphine oxides and triaziridinyl phosphine sulfides wherein each a: ring carbon atom is bonded to two members selected from the group consisting of alkyl, cycloalkyl, aryl, alkaryl and aralkyl radicals containing up to a total atoms for each aziridine ring and a diaziridinyl compound containing two aziridi joined through a divalent radical selected from the group consisting of carbonyj phenylphosphoryl, phenylthiophosphoryl, sulfoxyl and sulfonyl, each azi'ridine ri atom being bonded to two members selected from the group consisting of hydrogen radicals containing 1 to 1+ carbon atoms, said uncured polymer being .a polymer c selected from the group consisting of conjugated dienes having 1 to 12 carbon a1 molecule, aryl-substituted olefins, pyridine and quinoline derivatives containir one member of the group consisting of vinyl and alphamethyl vinyl, acrylic acid alkacrylic acid esters, vinylfuran and vinylcarbazole, and said acid group being g element selected from the group consisting of carbon, sulfur, silicon, selenium, 3 antimony, tellurium and arsenic.

' Column 16, 7 line 17, before "organo" insert an Signed and sealed this 16th day of April 1971;. I

(SEAL) 1 Attest:

' EDWARD M .FLLTCIER JR 0 C MARSHALL DANN Attes ting Officer 7, Commissioner of Pa UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,779,82h John E Mahan Dated Dec,' 18,

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 12, line 67, compound containing 3 aziridinyl groups per molecule and a compor containing only 2 aziridinyl groups per molecule" should read triaziridinyl compoz selected from the group consisting of triaziridinyl phosphine oxides and triaziridinyl phosphine sulfides wherein each aziridine ring carbon atom is bonded to two members SE from the group consisting of hydrogen, alkyl, cycloallayl, aryl, alkaryl, and aralkyl I containing up to a total of 20 carbon atoms for each aziridine ring, and a diaziridiny compound containing two aziridinyl radicals joined through a divalent radical selected from the group consisting of carbonyl, phenylphosphoryl, phenylthiophosphoryl s'ulfoxyl and sulfonyl, each aziridine ring carbon atom being bonded to two members selected. fro the group consisting of hydrogen and alkyl radicals containing 1 to A carbon atoms ColunnlS, line Z claim 12 should readz i method of preparing a solid propellant comp which comprises forming a mixture oi inorganic oxidizing salt and an uncured polymer containing at least 1 acid group per molecule, and curing said polymer by reacting ear. with a combination of a triaziridinyl compound selected from the group consisting of t 1 aziridinyl. phosphine oxides and triaziridinyl phosphine sulfides wherein each aziridin ring carbon atom is bonded to two members selected from the group consisting of hydrog alkyl, cycloalkyl, aryl, alkaryl and aralkyl radicals containing up to a total of 20 c atoms for each aziridine ring and a diaziridinyl compound containing two aziridinyl ra joined through a divalent radical selected from the group consisting of carbonyl, phenylphosphoryl, phenylthiophosphoryl, sulioxyl and sulfonyl, each aziridine ring car atom being bonded to two members selected from the group consisting of hydrogen and al radicals containing 1 to 1+ carbon atoms, said uncured polymer being .a polymer of a mo selected from the group consisting of conjugated dienes having b, to 12 carbon atoms pe molecule, aryl-substituted olefins, pyridine and quinoline derivatives containing at 1 one member of the group consisting of vinyl and alphamethyl vinyl, acrylic acid esters alkacrylic acid esters, vinylfuran and vinylcarbazole, and said acid group being of an element selected from the group consisting of carbon, sulfur, silicon, selenium, tin, 1 antimony, tellurium and arsenic.

Y Column 16, I line 17, before "organo" insert an Signed and sealed this 16th day of April 19714.. t

, EAL) Attest:

f EDWARD M.FLETCHER,JR 4 a C MARSHALL DANN Attesting Officer Commissioner of Patents 

2. The composition of claim 1 wherein said uncured polymer is a liquid polymer containing 1 to 4 of said acid groups terminally positioned on the molecule.
 3. The composition of claim 1 wherein said uncured polymer is a copolymer of said monomer with an unsaturated carboxylic acid having a maximum of 36 carbon atoms, from 1 to 4 double bonds, and from 1 to 2 carboxy groups per molecule.
 4. A solid propellant composition comprising an oxidant of inorganic oxidizing salt and a binder of synthetic solid polymer formed by reacting in admixture with said salt an uncured polymer of a monomer selected from the group consisting of conjugated dienes having 4 to 12 carbon atoms per molecule, aryl-substituted olefins, pyridine and quinoline derivatives containing at least one member of the group consisting of vinyl and alphamethylvinyl, acrylic acid esters, alkacrylic acid esters, vinylfuran and vinyLcarbazole, said uncured polymer containing per molecule at least one acid group of an element selected from the group consisting of carbon, sulfur, silicon, selenium, tin, antimony, tellurium, and arsenic with a combination of a trifunctional material having the formula
 5. The composition of claim 4 wherein said uncured polymer is a liquid polymer of a conjugated diene having 4 to 12 carbon atoms per molecule and contains 2 to 4 terminal carboxy groups.
 6. The composition of claim 4 wherein said uncured polymer is a copolymer of a conjugated diene having from 4 to 12 carbon atoms per molecule with an unsaturated carboxylic acid having a maximum of 36 carbon atoms, from 1 to 5 double bonds and from 1 to 2 carboxyl groups.
 7. A solid propellant composition comprising about 75 to 90 weight per cent inorganic oxidizing salt and about 10 to 25 weight per cent of a synthetic solid polymer formed by reacting in admixture with said salt an uncured polymer of a conjugated diene having from 4 to 12 carbon atoms per molecule, said uncured polymer containing at least one carboxyl group per molecule, with at least about a stoichiometric amount based on the acid equivalents of a combination curative containing 10 to 90 weight per cent of a trifunctional material having the formula
 8. The composition of claim 7 wherein said polymer is a liquid polymer of a conjugated diene having 4 to 12 carbon atoms per molecule and contains 2 to 4 terminal carboxy groups.
 9. The composition of claim 8 wherein said conjugated diene is butadiene, said trifunctional material is tri(2-methyl-1-aziridinyl) phosphine oxide and said difunctional material is phenyl-bis(2-methyl-1-aziridinyl) phosphine oxide.
 10. The composition of claim 7 wherein said salt is ammonium perchlorate, said polymer is polybutadiene prepared in the presence of an organodilithium initiator and containing two terminal carboxy groups per molecule, said trifunctional material is tri(2-methyl-1-aziridinyl) phosphine oxide, and said difunctional material is bis(1,2-propylene)-1,3-urea.
 11. The composition of claim 7 wherein said salt is ammonium perchlorate, said polymer is polybutadiene prepared in the presence of an organodilithium initiator and containing two terminal carboxy groups per molecule, said trifunctional material is tri(2-methyl-1-aziridinyl) phosphine oxide, and said difunctional material is bis(2-methyl-1-aziridinyl) sulfoxide.
 12. A method of preparing a solid propellant composition which comprises forming a mixture of inorganic oxidizing salt and an uncured polymer containing at least one acid group per molecule, and curing said polymer by reacting same with a combination of a compound containing 3 aziridinyl groups per molecule and a compound containing only 2 aziridinyl groups per molecule, said uncured polymer being a polymer of a monomer selected from the group consisting of conjugated dienes having 4 to 12 carbon atoms per molecule, aryl-substituted olefins, pyridine and quinoline derivatives containing at least one member of the group consisting of vinyl and alphamethylvinyl, acrylic acid esters, alkacrylic acid esters, vinyl-furan and vinylcarbazole, and said acid group being of an element selected from the group consisting of carbon, sulfur, silicon, selenium, tin, antimony, tellurium, and arsenic.
 13. A method of preparing a solid propellant composition which comprises forming a mixture of an inorganic oxidizing salt, an uncured polymer of a monomer selected from the group consisting of conjugated dienes having 4 to 12 carbon atoms per molecule, aryl-substituted olefins, pyridine and quinoline derivatives containing at least one member of the group consisting of vinyl and alphamethylvinyl, acrylic acid esters, alkacrylic acid esters, vinylfuran and vinylcarbazole, said uncured polymer containing per molecule at least one acid group of an element selected from the group consisting of carbon, sulfur, silicon, selenium, tin, antimony, tellurium, and arsenic a trifunctional material having the formula
 14. The composition of claim 13 wherein said uncured polymer is a liquid polymer containing 1 to 4 of said acid groups terminally positioned on the molecule.
 15. The method of claim 13 wherein said uncured polymer is a copolymer of said monomer with an unsaturated carboxylic acid having a maximum of 36 carbon atoms, from 1 to 5 double bonds and from 1 to 2 carboxyl groups.
 16. A method of preparing a solid propellant composition which comprises forming a mixture containing about 75 to 90 weight per cent inorganic oxidizing salt, about 10 to 25 weight per cent of a liquid polymer of a conjugated diene containing 4 to 12 carbon atoms per molecule, said polymer having been prepared in the presence of organo dilithium initiator and containing two terminal carboxy groups per molecule, and at least about a stoichiometric amount based on the acid equivalents of a combination curative containing 10 to 90 weight per cent of a trifunctional material having the formula
 17. The method of claim 16 wherein said conjugated diene is butadiene, said trifunctional material is tri(2-methyl-1-aziridinyl) phosphine oxide and said difunctional material is phenyl-bis(2-methyl-1-aziridinyl) phosphine oxide.
 18. The method of claim 16 wherein said conjugated diene is butadiene, said trifunctional material is tri(2-methyl-1-aziridinyl) phosphine oxide and said difunctional material is bis(1-2-propylene)-1,3-urea.
 19. The method of claim 16 wherein said mixture is poured as a slush into a rocket case and cured in situ. 